Cathodically protected water storage tanks



Dec. 30, 1958 RfJ. SUTTON 2,866,742

CATHODICALLY PROTECTED WATER STORAGE TANKS Filed June 29, 1956 2 Sheets-Sheet 1 INVENToR. Raben* J Sam BY Dec. 30, 1958 R. J. su'r'roN 2,866,742

CATHODICALLY PROTECTED WATER STORAGE TANKS Filed June 29, 1956 2 Sheets-Sheet 2 CATHODICALLY PRTECTED WATER STORAGE TANKS Roberti` Sutton, Chicago, Ill., assignor to General Electric Company, acorporation of New `:York

Application .inne 29, 1956; SeriaLNo. 594,859 l 7 Claims. (Cl. 204-197) The present invention relates to water storageV tanks, and more particularly to such tanks especially designed for use in water heaters, orl the like.

It isa general object of the invention to provide a, water storage tank that incorporates an improved liner arrangement that resists the. corrosive attack of waterl containing such common` corrosive agents as CO2, O2, Cl, S04, etc., in the pH range below about 9.0.

Another object of the invention is to provide a water.l storage tank that comprises a hollow. body formed of steel, a primary liner formed of zinc and` intimately bonded to the interior surface ofthe body, and a secondary liner formed of hydraulic cement andy arranged in contact and in covering vrelationwithonly the interior surface of the primary liner..

A further object of the invention isto provide a water storage tank of the character described, wherein the hydraulic cement ofthe secondary liner essentially coma portion of prises oxides of silicon and alkali earthmetals, so that the secondary liner Supplies small amountsof alkali earth metalcations to the water stored in the body.

A further object of the invention is to provide a-Water storage tank ofthe character described,vwherein the area of the primary liner is commensurate with that of the body and has a thickness of only several mils, and wherein the area of the secondary liner is commensurate with only amajor portion of thatof the primary liner and has a thickness only in the` general range 125 to 250 mils, whereby the water storage tank is givenelfective corro,-

sive protection with minimumcamounts of materialsJ in` the respective primary and secondary liners.

A stillfurther object ofthe invention is to provide a water storage tank of the character described, wherein the thermalmass of the secondary liner formed of concrete is` commensurate with that of the body formed of steel, whereby the Water storage tankis especially adapted for use in awater heater, or the like.

Further features of the-invention pertain tothe particular arrangementof the elements yof the water storage tank, whereby the above-outlined and` additional operating features thereof are attained.

The invention, both as to its organization andmethod of operation, togetherl with further objects and advantages thereof, will best be understood by, reference to the following specication taken in connection with the accompanying drawings, in which:

Figure l is a side elevational view,lpart1y broken away, ofthey water storage tank incorporated in an electric water heater and embodyingthe present invention;

Fig. 2 is a greatly enlarged fragmentary vertical sectional view ofthe ,Upper portion of the water. storage tank, illustrating the construction thereof at the junction4 betweenthe upper end of the tubular side Wall and the top header; v

Fig. 3 is a greatly enlarged fragmentary verticalv sectional view: of the lowerl portion of the water storage tank, illustrating the construction thereof at the junction :attentatiV` net.` 39.1958.

between the. lower, end. of! the tubular. side. wall, and; the bottom header; and

Fig. v4 is a side elevationaljyiew, partly brokeiraway,y

of a modified form of the water storagetank,

Referring now to Fig. 1,1 ofv the drawings,l there. is`

illustrated'the watern storage tankilofjan electric water. heater andembodying the features ofjthepresent invenf tion. The tank 10` comprises.anupstanding body 1 1.' formed of steel and. includinga,tub ular` s idjey u /all.1 2,"`a4 bottom header 13` carrying a. threaded'waterc inlet` Spud; 14, anda top header. 15 carrying@ threadedI water outlet4 spud 16; Alsothe bottom header, 13' carries an inlet water diffuser structurek 17 'disposedinthe lower'portion;

of the body 11 for the usual; purpose ofpreventin'g mi2(- ing ofthe cold incominglwater and the hot storedi water in the tank 10. Alsothe exteriorsurfaceofgthe, body 1.2v`

carrieslower and upper, electric heatingelements18andf 19 that are ofthe wrap-around type and that may beI of the construction` disclosed i n U'. Sg Patentu No. 2,452,214, granted on October 26, 1,948, toA Oliver G'.

Vogel and Francis E. Kirk.

As best illustrated' in Figs, 2 and 3; the interior surfaces of the tubular side wall 12.,l the bottom header 1,3"

and the top` header 15V are.p rovided'yvithA a continuous primary liner Ztl formed'of zinc, and/alsubstantially continuous outer coating 21 formed ofzincgand` preferably the primary liner 2@ and the outer coating. 21 are formed by hot` d ip galvanizingyas explainedmore fully below.` Also the interior surfaces of the p rilnaryflitierl 20 carry a continuous secondary liner 22j formed of' concrete. In the arrangement, the primary liner 20'. isY intimately bonded to the interior surfacesothe tubularside wall 12, the bottom header 1'3 and theI top header 15` and' commensurate in' area therewith,l whereby these interiorsurfaces are vcompletely covered by the, primary liner 20; The secondary linerv 22 is bonded to .the interiorsurfaces ofthe primary liner Ztl'overlyingrtheup'per portion ofthe tubular side walll`12` and the top header 15 and commensurate, in area, therewith;y whereby only theseinterior` surfacesof the primaryliner 2l) are covered by the secondary liner 22.1 Accordingly, a major portion' of,` the interior surfaces ofthe primary liner Ztlis coveredv by the secondary liner 22; leavinguncoveredA a minor portion of" theinterior surfaces of the primary liner 20' overlying the lower portion of the tubular side wall'123andthebottom header v13s, as explained more fully below.

In the arrangement, the primary linear` 20 has athickness of only several mils, corresponding to a weight of.A Zinc of about 2 oz-./ft.2, has a thickness in the generalV range to 250 mils. Further, the steel plate of the body 11 may have a thickness of about125 mils.

The secondary linerl 2,2 is formedgof'concrete, as.previ. ously noted, and may comprise a 2:1, mix of avsuitable aggregate-for example, cru-shedA limestonef-and'hydram. Preferably the hydraulic cementcomprises,

lic cement. a suitable Portland cement, i. e. Atlas. A Portland cement of this character may have the following approximate composition by weight:

while the secondary linear 2,24

ticularly the compounds CazSi, CasSiO and Caz (AlQ 2.

In the settingup actio',.the tricalcium silicate appears to be especially important, as it forms gelatinous hydrates which gradually `harden and cement the crystals together.

Turning now to amethod of making the tank the individual `steel elements comprising the tubular side wall 12, the bottom header 13 and the top header 15 are first formed; the waterV inlet spud 14 is suitably welded into .thel central opening provided in the bottom header 13; the water diffusion structure 17 is suitably welded to the interior surface of the bottom header 13; and the water outletspud 16 is suitably welded into the central opening provided in the top header 15. The top header is thenpr'essed in a convex position into the upper end of the Vtubular side wall 12 and welded in lplace byV electric seam welding, as indicated at 31 in Fig. 2. i The top subassembly, including the tubular side 'wall l2, the top header `15 and. the spud 16is then galvaniz'edt produce the corresponding portions of the primary liner and the outer coating 21; and likewise, the bottom sub-assembly, including the bottom header 13, the spud 14 and the dituson structure 17, is then galvanized to produce the corresponding portions of the primary liner 20 and the outer coating 21. In these operations, `hot-dip galvanizing is recommended. Next, the secondary liner 22 is applied within the top subassembly; and conveniently the top subassembly may be rotated in an inverted position in a spinning machine and the required amount of concrete mix `is `poured or sprayed thereinto so that the secondary liner 22 is formed and distributed, as desired, by the rotation of the subassembly. After the configuration of the secondary liner 22 is thus established, but before the concrete thereof has completely` set-up, the top subassembly is removed from the spinning machine, and the lower portion of the interior surface of the primary liner 20 is cleaned in any suitable manner so as to remove therefrom any concrete that may be deposited thereon. When the concrete of the secondary liner 22 has thoroughly set, the bottom subassembly is pressed in a concave position into the lower end ofthe tubular side wall 12 and welded in place by electric seam welding, as indicated at 32 in Fig. 3. In this welding step, the heat developed effects fusion of the cooperating engaging portions of the primary liner 20, so that upon cooling and `resolidiieation the primary liner 20 is entirely continuous; and likewise, the heat developed effects fusion of the cooperating engaging portions of the outer coating 21, so that upon cooling and resolidication the outercoating 21 is substantially continuous.

In the manufacture of a water heater utilizing the tinished tank 10, the electric heating elements 18 and 19 are applied and secured in place; and ultimately this assembly is arranged in a heat-insulating jacket or casing, not shown.

In the use of the tank 10: the area of the secondary linear22 that is in contact with the water stored therein is materially greater than the area of the primary liner 20 in contact with the water stored therein; the secondary liner 22 supplies small amounts of alkali earth metal cations to the stored water tending to increase the pH thereof; and the secondary liner 22 is rendered anodic, while the primary liner 20 and the body 11 arerendered cathodic, when water is stored therein. Accordingly, the arrangement, when the primary liner 20 and the secondary liner` 22 is very advantageousto protect the steel body 11 against the corrosive attack of stored water containing corrosive `agents characteristic of city water in many soft-water areas, notwithstanding the facts that the primary `zinc liner 20 has a thickness of only several mils,` and the secondary concrete liner 22 has a thickness less than about VH'L Specifically, in this connection, it is noted that the protection that is atorded to the steel body 11 is greatlyin excess of that provided by the relatively thin primary zinc liner 20 andthe protection afforded the ssamm I primary liner 20 is greatly in excess of that provided by the relatively thin concrete liner 22; which composite protection is brought about by the electrolytic or galvanic phenomena previously mentioned, by virtue of the fact that the composite arrangement renders cathodic the steel body 11 and the primary zinc liner 20.

Also, it is mentioned that the arrangement of the tank 10 in a water heater is very advantageous by virtue of the circumstance that the heat-storage capacity of the concrete liner 22 is commensurate with that of the steelbody 11; whereby the thermal mass of the tank 10 is substantially twice that of a conventional water storage tank; which arrangement minimizes cooling of the mass of stored hot water incident to a draw-off of hot water for use.

Referring now to Fig. 4, a modified form of the water storage tank is illustrated and embodying the features of the present invention. The tank 110 is fundamentally of the same construction as the tank 10, previously described, and including the corresponding elements 111, 112, 113, etc. However, in this construction, the secondary concrete liner 122 is bonded to the interior surfaces of the primary zinc liner overlying the tubular side wall 112 and the adjacent peripheral portions of the bottom header 113 and the top header 115 and commensurate in area therewith; whereby only these interior surfaces of the primary liner 120 are covered by the secondary liner 122.

Turning now to a method of making the tank 110: the top subassembly and the bottom subassembly are produced and secured together to provide a composite container, in the manner previously explained, prior to the applicationrof the secondary concrete liner 122. At this time, the secondary liner 122 is applied within the completed tank 110; and conveniently the completed tank may be rotated in a substantially horizontal position in a spinning machine and the required amount of concrete mix is poured or sprayed thereinto through the spud 116 so that the secondary liner 122 is formed and distributed, as desired, by the rotation of the tank 110. After the secondary concrete liner 122 has been distributed and set-up, the finished tank 110 may be removed from the spinning machine.

The overall advantages and utility of the tank 110 are the same as described in conjunction with the tank 10.

In view of the foregoing, it is apparent that there has been provided in a steel water storage tank an improved primary-secondary liner arrangement that attords a ma imum protection against attack by water containing corrosive components, while utilizing substantially minimum quantity of protective materials in the respective primary and secondary liners employed in the arrangement.

While there has been described what is at present considered to be the preferred embodiment of the invention,

it will be understood that various modiications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A water storage tank comprising a hollow body formed of steel and including a tubular side wall and a pair of opposed end Walls, a primary liner formed of zinc and intimately bonded to the interior surfaces of said side Wall and said end walls, said primary liner being continuous and commensurate with the interior surfaces of said side wall and said end walls completely to cover the same, and a secondary liner in contact with the interior surface of said primary liner and formed of concrete, said secondary liner covering the major area of the interior surface of said primary liner and leaving uncovered the minor area of the interior surface of said primary liner, said uncovered minor area being at least substantially commensurate with the inside area of one of said end walls, said secondary liner supplying small amounts of alkali earth metal cations to the water stored in said body, and the area of said secondary liner in contact with the water stored in said body being materially greater than the area of said primary liner in contact with the water stored in said body.

2. The water storage tank set forth in claim 1, wherein said primary liner has a thickness of only several mils,

and said secondary liner has a thickness in the range y said secondary liner has a heat storage capacity cornmensurate with that of said body in order substantially to increase the thermal mass of said tank.

6. A water storage tank comprising a hollow body formed of steel and including a tubular side wall and a pair of opposed end walls, a primary liner formed of zinc and intimately bonded to the interior surfaces of said side wall and said end walls, said primary liner being continuous and commensurate with the interior surfaces of said side wall and said end walls completely to cover the same, and a secondary liner formed of concrete and in contact with the interior surfaces of said primer liner overlying one of said end walls and overlying a major portion of said side wall, the interior surfaces of said primary liner overlying the other of said end walls and overlying a minor portion of said side wall being uncovered by said secondary liner, said secondary liner supplying small amounts of alkali earth metal cations to the water stored in said body, and the area of said secondary liner in contact with the water stored in said body being materially greater than the area of said pri- 10 mary liner in contact with the water stored in said body.

7. The water storage tank set forth in claim 6, wherein said tank is normally arranged in an upstanding position and it is the interior surfaces of said primary liner overlying the bottom end wall and the lower portion of said 15 side wall that are uncovered by said secondary liner.

References Cited in the le of this patent UNITED STATES PATENTS London, Edward Arnold & Co., 1948, pp. 171, 328 and 329. 

1. A WATER STORAGE TANK COMPRISING A HOLLOW BODY FORMED OF STEEL AND INCLUDING A TUBULAR SIDE WALL AND A PAIR OF OPPOSED END WALLS, A PRIMARY LINER FORMED OF ZINC AND INTIMATELY BONDED TO THE INTERIOR SURFACES OF SAID SIDE WALL AND SAID END WALLS SAID PRIMARY LINER BEING CONTINUOUS AND COMMENSURATE WITH THE INTERIOR SURFACES OF SAID SIDE WALL AND SAID END WALLS COMPLETELY TO COVER THE SAME, AND A SECONDARY LINER IN CONTACT WITH THE INTERIOR SURFACE OF SAID PRIMARY LINER AND FORMED OF CONCRETE, SAID SECOND LINER COVERING THE MAJOR AREA OF THE INTERIOR SURFACE OF SAID PRIMER LINER AND LEAVING UNCOVERED THE MINOR AREA OF THE INTEIROR SURFACE OF SAID PRIMARY LINER, SAID UNCOVERED MINOR AREA BEING AT LEAST SUBSTANTIALLY COMMENSURATE WITH THE INSIDE AREA OF ONE OF SAID END WALLS, SAID SECONDARY LINER SUPPLYING SMALL AMOUNTS OF ALKALI EARTH METAL CATIONS TO THE WATER STORED IN SAID BODY, AND THE AREA OF SAID SECONDARY LINER IN CONTACT WITH THE WATER STORED IN SAID BODY BEING MATERIALLY GREATER THAN THE AREA OF SAID PRIMARY LINER IN CONTACT WITH THE WATER STORED IN SAID BODY. 